A standard press, for instance used with an injection-molding machine, comprises outside and inside end plates spanned by a plurality of tie or guide rods and at least one movable plate slidable along the rods between the plates. The movable plate and the inside end plate have confronting faces carrying respective mold parts or halves of similar tools, hence these two plates are also normally called mold plates. A ram is provided to press the movable mold plate with considerable force against the inside fixed mold plate during the molding or working operation. Since this ram is typically braced between the movable mold plate and the outside end plate, the tie rods must be extremely strong and well anchored in the end plates to withstand the resultant tension.
Frequently, however, it is necessary to use tool or mold parts that are so large that they cannot fit through the space between two adjacent rods. Thus at least one of the rods must be removed. Clearly making such a guide/tie rod removable and at the same time anchoring it very solidly is very difficult
In one known system of Engel (see Kunstoff-Plastics 2/88) a hydraulic drive unscrews a nut at the inside-plate end of the tie rod and the tie rod is then clamped in the movable plate. The movable plate is then backed away from the inside plate to pull out the tie rod. The tie rod is then unclamped, the movable plate advanced and then reclamped on the tie rod, and so on until the tie rod has been sufficiently retracted. Such a procedure is fairly cumbersome, requiring the massive movable plate to be moved, and also does not provide a high degree of anchoring of the tie rod when the press is in use.
In German patent document 2,455,702 of G. Myers et al (based on U.S. application No. 467,897 filed May 8, 1974) the openable tie rod, of which only one is needed in a normal machine, is unscrewed and stepped out as in the Engel system, but a complicated pincher-type clamp is used.
U.S. Pat. No. 3,673,849 of Voitsekhovsky et al has a system where all the tie rods can be unscrewed from one of the end plates, while U.S. Pat. No. 4,473,346 of Hehl shows an arrangement with a wedge-type clamp for the tie rods.
A complicated unscrewing/clamping system is seen in U.S. Pat. No. 3,465,387 of Martin, and various nut-type tie-rod fasteners and adjusters can be seen in German patent document 2,353,798 of P. Poncet (based on French 7,238,860 filed Oct. 27, 1972) and German Utility Model 1,974,739.
All the known systems are either quite complicated or offer insufficient anchoring for the tie rods. Few allow the tie rod to be uncoupled and withdrawn wholly automatically while still allowing it to be solidly anchored when the press is in use.